Turbo Kit Test TJ

Woodrow said:
I think a big point is that putting a slightly hotter cam with stiffer valve springs increases cam wear given the flat tappet (non-roller) lifter set up. This
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I remember reading about the zinc additive being required during breakin and recommended after breakin but I didn’t know why this was a thing for a stroker.

I thought some 4.6/4.7 builds included roller-style cams, but I don’t know what the cons might be for doing so. I had it in my head that I wouldn’t want a cam requiring stiffer springs if I did a stroker (but I’m also not sure if that thinking is logical or if it would undermine paying the extra coin for a stroker). I also don’t know if getting a nitrided cam helps alleviate wear concerns as well as doing the zinc additive.
 
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srimes said:
Turbo through the hood is bad ass. Double upgrade.
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FIFY

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I am not up to date on tar-bows like I used to be, but I wouldn't be surprised if that one is name brand. I'd fox with that Jeep. Was just making fun of people who are super sensitive about those fender types 😊
 
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Jezza said:
Should be more than enough for the stock engine.
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The previous talk of cams brings up a question. I assume you're building around a completely stock engine and intend for this to be a no cam, no springs required kind of set up, so are stock springs strong enough for say 10-12 psi at full boogie?
 
SkylinesSuck said:
What do springs have to do with how much boost you can run?
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The boost pressure blows on the back side of the valve and can blow the valve open if the springs aren't strong enough. With the 4.0 being a flat tappet engine, the spring rate is relatively low.
 
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I can honestly say I've never heard that before. Cam profile and rpm, sure, but I've never heard it being a factor for boost. All of my turbo experience has been on OHC motors might be a reason why, but I'm surprised to hear that. Gonna research it up a bit.
 
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BTW, did you mean intake valve instead of exhaust valve? I could see theoretically how the intake valve might be affected but can't wrap my head around how the exhaust valve would get hung open.

*Just considered maybe beck pressure from the turbo pushing on the exhaust valve?
 
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SkylinesSuck said:
*Just considered maybe beck pressure from the turbo pushing on the exhaust valve?
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I've never heard of back pressure effecting an exhaust valve in that way. I think there would have to be other problems to build back pressure to that level, maybe a waste gate slamming shut or something, but at that point you have other issues to worry about.
 
Correct me if I'm wrong, but I thought the pressure in the exhaust prior to the hot side turbine was almost always higher than what was getting crammed into the cold side when giving it the beans. If not, I can't see how you would logically get to the exhaust valve seeing boost and getting hung open compared to the intake. I'm just trying to wrap my head around it as I've run multiple motors (OHC though) with stock springs and 2 bar+ of boost with no issues save for trying up rev them over 8.5k lol.
 
I think something is getting crossed up. Boost can blow open an intake valve if the springs aren't strong enough to hold them shut. The exhaust valve/side will in no way be effected by this.
 
I just reread and was mistaken where I thought you said exhaust valve. I understand now you are talking about the intake valve. I'm still skeptical this is a practical issue but I'm keeping an open mind and using some Google-fu on the topic.
 
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I'm not sure where the valvetrain issues would start with high boost. I can tell you that it is above 20 as that is what I have run on my stock engine already.
 
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